Depolarizing mixture and method of preparing same



Patented Jan. 8, 1924.

UNITED STATES 1,480,533 PATENT OFFICE.

WILLIAM R. CLYMER, OF CLEVELAND, OHIO, ASSIGNOR T NATIONAL CARBON COM- PANY, INC., A CORPORATION OF NEW YORK.

DEPOLARIZING MIXTURE AND METHOD OF PREIARING SAME.

No Drawing.

of de olarizing efliciency in ry cells of the Le C anch type. The invention relates also to methods of preparing such mixtures.

Depolarizing mixtures for Le \Jl'anch cells are now commonly repared by commingling manganese dioxld, natural or artificial, with either graphite or non-graphitic carbon, the components being preliminarily ground and graded to a degree of fineness suitable for the pur ose in view, and the mixture being usual y mixed with saI ammoniac and moistened with electrolyte solution, and either tam-ped into the cans around a carbon electrode or molded into so-called bobbins.

According to the present invention the carbon and manganese dioxid components of such depolarizing mixtures are subjected to a joint milling or equivalent operation, thepreferred milling conditions being as herein below described. Sal ammoniac is added to the resulting milled mixture which is then preferably moistened with water or with electrolyte solution, and either tamped into the battery or molded into bobbin form according to the type of battery desired.

I have discovered that for dry battery purposes the joint milling of carbon and manganese dioxid ields a product materiall higher in dep orazing value than any pro not which I have been able to obtain by singly grinding or milling the components for an equal period of time, or to the same general order of fineness, and thereafter thoroughly commingling the ground materials. I attribute this effect in part to the interaction during the millin operation of two substances differing rather widely in hardness and in other ualities affecting the grinding operation, an in part to the physical state of association of the components of the milled mixture.

My preferred mixture consists of native Application filed September 17, 1920. Serial No. 410,923.

manganese dioxid ore or pyrolusite, the quality common] known as Phillipsbur pyrolusite having n found well ada te for the purpose; and carbon derived rom petroeum coke, previousl calcined electrically at about 1600 1800 (i matters are expelled quires, with minimum current input, the desirable degree of electrical conductivity for the particular purpose in view. My invention is not limited however to the choice of materials of these particular grades or qualities.

A preferred procedure in accordance with my invention is as follows, it being understood that the invention is not restricted to the specific manipulations or to the particular quality or pro ortion of components described by way of example:

Petroleum coke, calcined as above described and crushed in a Jefirey or other pulverizer to pass a one-fourth inch opening is mixed with pyrolusite, previously crushed to pass a 30 mesh screen, as for example by Sturtevant rolls. The resulting mixture is then milled for several hours in a pebble mill or equivalent device for mechanical reduction. Either dry or wet milling may be employed, the formed being preferred. Satisfactory results have been obtained for instance by 4-7 hours milling in an Abbe #7 pebble mill, at about 36 revolutions per minute. Under these conditions, the carbon, being the softer component, or at any rate undergoing the more rapid reduction in size, appears to coat the pyrolusite particles, with the result that there is established between the carbon and pyrohisite components an extreme intimacy of contact as well as a highly favorable surface-exposure relation. Also, the resulting mix possesses a relatively high absorptive capacity for electrolyte solution.

Batteries prepared from these mixtures have shown service results materially better than are obtainable from the same materials separately ground and intimately mixed; and also service'results equal to or better than those obtainable with graphite or other expensive forms of carbon of extreme finencss.

When the raw materials are pyrolusite and highly calcined petroleum coke, and the dry batteries are of the so-called midget type, a mix ratio approximately 2 parts of pyrowhereby all volatile and the carbon ac- 'bon in any particular proportions, especially since these prportions may vary considerably according to the nature of gradeof the manganese dioxid and carbon components used, and with-the size and service requirementsof the cells in which the mix is used.

The desirable state of division of the components of the mixture to-be milled will naturally vary with the quality or character of these components, and also in a measure with the milling facilities available. As a general rule however the best results are secured when the carbon is initially in a coarser state of subdivisionthan the pyrolusite. In the milled product, on the other hand, a considerable proportion at least of the carbon component exists in a very fine state of subdivision, the rate of subdivision being greatly accelerated by the presence of the harder particles of pyrolusite.

While I have referred above to highly calcined petroleum coke and native manganese dioxid as the commercially desirable raw materials for use in connection with the present invention, it is to be understood that other forms of carbon and manganese dioxid may be employed without departure from my invention. Thus for example the pyrolusite may be replaced wholly or in part by artificial manganese dioxid; and similarly the highly calcined petroleum coke may be replaced wholly or in part by other fully shrunk and suitably conductive forms of carbon, or by graphite.

I claim I 1. Method of preparing a battery dcpolarizer comprising subjecting a mixture containing pyrolusite, and conductive carbon to a milling operation until the desired depolarizing efficiency is attained.

2. Method of preparing a battery depolarizer comprising subjecting a mixture containing pyrolusite and conductive carbon to a milling operation until the desired depolarizing efiiciency! is attained, the carbon particles being initially coarser than the manganese dioxi'd particles.

3. Method of preparing a battery depolarizer comprising subjecting a mixture containing pyrolusite and highly calcined petroleum coke to-a milling operation until the desired depolarizing efiiciency is attained.

4.. Method of preparing a battery (lepolarizer comprising subjecting a mixture containing pyrolusite and highly calcined petroleum coke to a milling operation until the desired depolarizing efliciency is attained, the petroleum coke particles being iiliitially coarser than the pyrolusite partic es. 1

5. A depolarizing mixture for electric batteries comprising the product of the joint milling of pyrolusite and conductive carbon, said mixture comprising particles of the respective components in the intimate physical association resulting from said milling operation.

6. A depolarizing mixture for electric batteriescomprising the product of the joint milling of pyrolusite and highly calcined petroleum coke, said mixture comprising particles of the respective components in the intimate physical association resulting from said milling operation.

7. A depolarizing mixture for electric batteries comprising particles of pyrolusite superficially coated with highly conductive carbon. I

In testimony whereof, I aflix my signature.

WILLIAM R. CLYMER. 

